A ram-air intake is any air intake system which uses the air pressure created by vehicle motion to increase the air pressure inside of the intake manifold on an engine.
For example, a ramjet eliminates many moving parts by using the forward motion to compress incoming air.
Ram-air systems are used on some high performance and race cars. These allow a greater volume of intake air. A ram-air intake will also provide cooler air, as outside air rather than hot air from the engine compartment is used. However, Fluid Dynamics cannot support claims that a higher volume of intake air is accomplished at speeds attainable by high performance and race cars. Forcing a large volume of air into a cone by motion alone is not possible.